CNN's Randi Kaye reports on dogs that are specially trained to detect bomb vapors over incredible distances. She traveled to Auburn University to see how the program works.

Researchers call them vapor wake dogs because of their ability to find explosives before bombs are placed somewhere – like inside a backpack on a person moving through a crowd. The skill is so unique that the university hopes to patent it.

Puppies begin training at an early age, and the school has its own breeding program. They typically work with Labradors and Spaniels. Paul Hammond, whose company IK9 is working with Auburn, explains that a dog's olfactory system is 220 million scent cells compared to a human's five million scent cells.

CNN did an experiment in an Alabama Mall with the help of Auburn's canine handlers. A man carried a bag containing explosives inside a pressure cooker, which is similar to the device used in the deadly Boston Marathon attack. The dog passed the test by catching the scent and indicating what he found.